Jang Song Chol: Named by the US Treasury as a Komid representative in Russia and a government official.

Kim Yong Chol: An official of the North Korean government, according to the US, and a Komid representative in Iran.

Ryu Jin and Kang Ryong: Komid officials and members of the North Korean government who are operating in Syria, according to the US.

White House officials told reporters the move was in response to the Sony hack, but the targets of the sanctions were not directly involved.

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Media captionSpeaking before Christmas, President Obama said the Sony hack was "an act of cyber-vandalism"

Instead, the sanctions are designed to further isolate North Korea's defence industry as deterrent for future cyber-attacks.

The FBI and President Obama have previously said they believe North Korea was behind the cyber-attack, although some cyber-security experts have cast doubt on this.

However, a senior White House official said it was extremely rare for the US to attribute cyber-attacks, and it was only done so because of the destructive nature of the attack, and because the White House saw it as "crossing a threshold".

The BBC's Kevin Kim in Seoul says North Korea has denied any involvement in the hacking and is therefore likely to respond angrily to the latest measures.

However, he says, as there is little trade between North Korea and the US the latest measures are unlikely to have any great effect, and will simply be heavy on symbolism.

Hack effect

Sony was embarrassed after a group calling itself Guardians of Peace leaked data from its computers, exposing emails and personal details.

Image copyrightEPAImage caption
The Interview was later distributed online

The group later threatened cinema chains planning to screen Sony's satirical North Korea comedy, The Interview.

Oblique references to the 9/11 terror attacks prompted the cancellation of the film's nationwide release. A small number of independent cinemas did screen the film, and it was released online.

Announcing Friday's sanctions, the US said the apparent effort to stifle the movie release was part of the justification for the new restrictions.

"We take seriously North Korea's attack that aimed to create destructive financial effects on a US company and to threaten artists and other individuals with the goal of restricting their right to free expression," the White House said in a statement.

"Today's actions are the first aspect of our response."

North Korea has blamed the US for lengthy internet outages in the country last week.

Sony hack: The Interview saga

The Interview features James Franco and Seth Rogen as two journalists granted an audience with Mr Kim. The CIA then enlists the pair to assassinate him.